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United States Patent |
5,523,439
|
Ogihara
,   et al.
|
June 4, 1996
|
Process for preparing silacyclohexane compounds
Abstract
Processes for selectively preparing silacyclohexane compounds of a trans
form from diarylsilacyclohexane compounds of the general formula
##STR1##
wherein Ar and Ar' independently represent a phenyl group or a tolyl
group, and Q represents a group of the type indicated below
##STR2##
The diarylsilacyclohexanes are converted to dihalosilacyclohexanes and
then to hydrohalosilacyclohexanes directly or via dialkoxylation and/or
reduction step. The hydrohalosilacyclohexane are finally reacted with
organometallic compounds having a group, Q', of the type indicated below
##STR3##
to obtain silacyclohexane compounds of the general formula
##STR4##
wherein Q' and Q have, respectively, the groups indicated hereinabove.
Inventors:
|
Ogihara; Tsutomu (Niigata-ken, JP);
Shimizu; Takaaki (Niigata-ken, JP);
Kinsho; Takeshi (Niigata-ken, JP);
Kaneko; Tatsushi (Niigata-ken, JP)
|
Assignee:
|
Shin-Etsu Chemical Co., Ltd. (Tokyo, JP)
|
Appl. No.:
|
511816 |
Filed:
|
August 7, 1995 |
Foreign Application Priority Data
Current U.S. Class: |
556/406; 204/157.44; 204/157.45; 204/157.64; 204/157.74 |
Intern'l Class: |
C07F 007/08; C07F 007/18 |
Field of Search: |
556/406
204/157.44,157.45,157.64,157.74
|
References Cited
U.S. Patent Documents
4973723 | Nov., 1990 | Cawthorn et al. | 556/406.
|
5454977 | Oct., 1995 | Shimizu et al. | 556/406.
|
Primary Examiner: Shaver; Paul F.
Attorney, Agent or Firm: Lowe, Price, LeBlanc & Becker
Claims
What is claimed is:
1. A process for preparing a silacyclohexane compound, which comprises the
steps of:
(1) subjecting a diarylsilacyclohexane compound of the following general
formula
##STR62##
wherein Ar and Ar' independently represent a phenyl group or a tolyl
group, and Q represents a group of the following general formula
##STR63##
in which
##STR64##
independently represent
##STR65##
wherein Y.sub.3 represents H, F or CH.sub.3 ;
##STR66##
represents
##STR67##
wherein Y.sub.1 and Y.sub.2 independently represent H, F or Cl; X
represents R or OR, in which each R represents a linear alkyl group having
from 1 to 10 carbon atoms, a branched alkyl group having from 3 to 8
carbon atoms, an alkoxyalkyl group having from 2 to 7 carbon atoms or an
alkenyl group having from 2 to 8 carbon atoms, CN, F, Cl, CF.sub.3,
CF.sub.2 Cl, OCF.sub.3, OCHF.sub.2, OCF.sub.2 Cl, OCHFCl, (O).sub.m
CT.dbd.CX.sub.1 X.sub.2, or O(CH.sub.2).sub.r (CF.sub.2).sub.s X.sub.3
wherein m is a value of 0 or 1, T and X.sub.1 independently represent H, F
or Cl, X.sub.2 represents F or Cl, r and s are, respectively, a value of
0, 1 or 2 provided that r+s=2, 3 or 4, and X.sub.3 represents F or Cl; and
i1, i2 and i3 are, respectively, 0 or 1 provided that i1+i2+i3=1 and j1,
j2 and j3 are, respectively, a value of 0, 1 or 2 provided that
j1+j2+j3=0, 1 or 2, to conversion into a dihalosilacyclohexane compound of
the following general formula
##STR68##
wherein each W represents a halogen; (2) subjecting the resultant
dihalosilacyclohexane compound to further reaction with an alcohol of the
general formula, R'OH, wherein R' represents a linear alkyl group having
from 1 to 10 carbon atoms or a branched alkyl group having from 3 to 8
carbon atoms, thereby obtaining a dialkoxysilacyclohexane compound of the
following general formula
##STR69##
(3) reducing the dialkoxysilacyclohexane compound to obtain a
dihydrosilacyclohexane compound of the following general formula
##STR70##
(4) subjecting the dihydrosilacyclohexane compound to monohalogenation to
obtain a hydrohalosilacyclohexane compound of the following general
formula
##STR71##
wherein W represents a halogen; and (5) subjecting the
hydrohalosilacyclohexane compound to reaction with an organometallic
reagent of the general formula, Q'--M, wherein (a) Q' represents a group
of the following general formula
##STR72##
in which
##STR73##
represents
##STR74##
wherein Y.sub.3 represents H, F or CH.sub.3 ;
##STR75##
represents
##STR76##
wherein Y.sub.1 and Y.sub.2 independently represent H, F or Cl; X'
represents R or OR, in which each R represents a linear alkyl group having
from 1 to 10 carbon atoms, a branched alkyl group having from 3 to 8
carbon atoms, an alkoxyalkyl group having from 2 to 7 carbon atoms or an
alkenyl group having from 2 to 8 carbon atoms, CN, F, Cl, CF.sub.3,
CF.sub.2 Cl, OCF.sub.3, OCHF.sub.2, OCF.sub.2 Cl, OCHFCl, (O).sub.m
CT.dbd.CX.sub.1 X.sub.2, or O(CH.sub.2).sub.r (CF.sub.2).sub.s X.sub.3
wherein m is a value of 0 or 1, T and X.sub.1 independently represent H, F
or Cl, X.sub.2 represents F or Cl, r and s are, respectively, a value of
0, 1 or 2 provided that r+s=2, 3 or 4, and X.sub.3 represents F or Cl; and
k1 and k2 are independently a value of 0 or 1 provided that k1+k2=1, m1
and m2 are independently represent a value of 0, 1 or 2 provided that
m1+m2=0, 1 or 2; and (b) M represents MgP or ZnP wherein P represents a
halogen, thereby obtaining a silacyclohexane compound of the following
general formula
##STR77##
wherein Q' and Q have, respectively, the same meanings defined above.
2. A process according to claim 1, wherein in step (1), the
diarylsilacyclohexane compound is converted to the dihalosilacyclohexane
compound by reaction with an electrophilic reagent.
3. A process according to claim 1, wherein the conversion of the step (1)
is effected by addition of a Lewis acid or by irradiation of actinic
light.
4. A process according to claim 3, wherein said Lewis acid is solid and is
removed prior to the step (5).
5. A process according to claim 1, wherein the alcohol used in the step (2)
is a lower alcohol.
6. A process for preparing a silacyclohexane compound comprising the steps
of:
(1) subjecting a diarylsilacyclohexane compound of the following general
formula
##STR78##
wherein Ar and Ar' independently represent a phenyl group or a tolyl
group, and Q represents a group of the following formula
##STR79##
in which
##STR80##
independently represent
##STR81##
wherein Y.sub.3 represents H, F or CH.sub.3 ;
##STR82##
represents
##STR83##
wherein Y.sub.1 and Y.sub.2 independently represent H, F or Cl; X
represents R or OR, in which each R represents a linear alkyl group having
from 1 to 10 carbon atoms, a branched alkyl group having from 3 to 8
carbon atoms, an alkoxyalkyl group having from 2 to 7 carbon atoms or an
alkenyl group having from 2 to 8 carbon atoms, CN, F, Cl, CF.sub.3,
CF.sub.2 Cl, OCF.sub.3, OCHF.sub.2, OCF.sub.2 Cl, OCHFCl, (O).sub.m
CT.dbd.CX.sub.1 X.sub.2, or O(CH.sub.2).sub.r (CF.sub.2).sub.s X.sub.3
wherein m is a value of 0 or 1, T and X.sub.1 independently represent H, F
or Cl, X.sub.2 represents F or Cl, r and s are, respectively, a value of
0, 1 or 2 provided that r+s=2, 3 or 4, and X.sub.3 represents F or Cl; and
i1, i2 and i3 are, respectively, a value of 0 or 1 provided that
i1+i2+i3=1 and j1, j2 and j3 are, respectively, a value of 0, 1 or 2
provided that j1+j2+j3=0, 1 or 2, to conversion into a
dihalosilacyclohexane compound of the following general formula
##STR84##
wherein each W represents a halogen; (2) reducing the
dihalosilacyclohexane compound to obtain a dihydrosilacyclohexane compound
of the following general formula
##STR85##
(3) subjecting the dihydrosilacyclohexane compound to monohalogenation to
obtain a hydrohalosilacyclohexane compound of the following general
formula
##STR86##
wherein W represents a halogen; and (4) subjecting the
hydrohalosilacyclohexane compound to reaction with an organometallic
reagent of the general formula, Q'--M, wherein (a) Q' represents a group
of the following formula
##STR87##
in which
##STR88##
represents
##STR89##
wherein Y.sub.3 represents H, F or CH.sub.3 ;
##STR90##
represents
##STR91##
wherein Y.sub.1 and Y.sub.2 independently represent H, F or Cl; X'
represents R or OR, in which each R represents a linear alkyl group having
from 1 to 10 carbon atoms, a branched alkyl group having from 3 to 8
carbon atoms, an alkoxyalkyl group having from 2 to 7 carbon atoms or an
alkenyl group having from 2 to 8 carbon atoms, CN, F, Cl, CF.sub.3,
CF.sub.2 Cl, OCF.sub.3, OCHF.sub.2, OCF.sub.2 Cl, OCHFCl, (O).sub.m
CT.dbd.CX.sub.1 X.sub.2, or O(CH.sub.2).sub.r (CF.sub.2).sub.s X.sub.3
wherein m is a value of 0 or 1, T and X.sub.1 independently represent H, F
or Cl, X.sub.2 represents F or Cl, r and s are, respectively, a value of
0, 1 or 2 provided that r+s=2, 3 or 4, and X.sub.3 represents F or Cl; and
k1 and k2 are independently a value of 0 or 1 provided that k1+k2=1, m1
and m2 are independently represent a value of 0, 1 or 2 provided that
m1+m2=0, 1 or 2; and (b) M represents MgP or ZnP wherein P represents a
halogen, thereby obtaining a silacyclohexane compound of the following
general formula
##STR92##
wherein Q' and Q have, respectively, the same meanings defined above.
7. A process according to claim 6, wherein in step (1), the
diarylsilacyclohexane compound is converted to the dihalosilacyclohexane
compound by reaction with an electrophilic reagent.
8. A process according to claim 6, wherein the conversion of the step (1)
is effected by addition of a Lewis acid or by irradiation of actinic
light.
9. A process for preparing a silacyclohexane compound comprising the steps
of:
(1) subjecting a diarylsilacyclohexane compound of the following general
formula
##STR93##
wherein Ar and Ar' independently represent a phenyl group or a tolyl
group, and Q represents a group of the following general formula
##STR94##
in which
##STR95##
independently represent
##STR96##
wherein Y.sub.3 represents H, F or CH.sub.3 ;
##STR97##
represents
##STR98##
wherein Y.sub.1 and Y.sub.2 independently represent H, F or Cl; X
represents R or OR, in which each R represents a linear alkyl group having
from 1 to 10 carbon atoms, a branched alkyl group having from 3 to 8
carbon atoms, an alkoxyalkyl group having from 2 to 7 carbon atoms or an
alkenyl group having from 2 to 8 carbon atoms, CN, F, Cl, CF.sub.3,
CF.sub.2 Cl, OCF.sub.3, OCHF.sub.2, OCF.sub.2 Cl, OCHFCl, (O).sub.m
CT.dbd.CX.sub.1 X.sub.2, or O(CH.sub.2).sub.r (CF.sub.2).sub.s X.sub.3
wherein m is a value of 0 or 1, T and X.sub.1 independently represent H, F
or Cl, X.sub.2 represents F or Cl, r and s are, respectively, a value of
0, 1 or 2 provided that r+s=2, 3 or 4, and X.sub.3 represents F or Cl; and
i1, i2 and i3 are, respectively, a value of 0 or 1 provided that
i1+i2+i3=1 and j1, j2 and j3 are, respectively, a value of 0, 1 or 2
provided that j1+j2+j3=0, 1 or 2, to conversion into a
dihalosilacyclohexane compound of the following general formula
##STR99##
wherein each W represents a halogen; (2) reducing the
dihalosilacyclohexane compound under conditions sufficient to obtain a
hydrohalosilacyclohexane compound of the following general formula
##STR100##
wherein W has the same meaning as defined above; and (3) subjecting the
hydrohalosilacyclohexane compound to reaction with an organometallic
reagent of the general formula, Q'--M, wherein (a) Q' represents a group
of the following general formula
##STR101##
in which
##STR102##
represents
##STR103##
wherein Y.sub.3 represents H, F or CH.sub.3 ;
##STR104##
represents
##STR105##
wherein Y.sub.1 and Y.sub.2 independently represent H, F or Cl; X'
represents R or OR, in which each R represents a linear alkyl group having
from 1 to 10 carbon atoms, a branched alkyl group having from 3 to 8
carbon atoms, an alkoxyalkyl group having from 2 to 7 carbon atoms or an
alkenyl group having from 2 to 8 carbon atoms, CN, F, Cl, CF.sub.3,
CF.sub.2 Cl, OCF.sub.3, OCHF.sub.2, OCF.sub.2 Cl, OCHFCl, (O).sub.m
CT.dbd.CX.sub.1 X.sub.2, or O(CH.sub.2).sub.r (CF.sub.2).sub.s X.sub.3
wherein m is a value of 0 or 1, T and X.sub.1 independently represent H, F
or Cl, X.sub.2 represents F or Cl, r and s are, respectively, a value of
0, 1 or 2 provided that r+s=2, 3 or 4, and X.sub.3 represents F or Cl; and
k1 and k2 are independently a value of 0 or 1 provided that k1+k2=1, m1
and m2 are independently represent a value of 0, 1 or 2 provided that
m1+m2=0, 1 or 2; and (b) M represents MgP or ZnP wherein P represents a
halogen, thereby obtaining a silacyclohexane compound of the following
general formula
##STR106##
wherein Q' and Q have, respectively, the same meanings defined above.
10. A process according to claim 9, wherein in step (1), the
diarylsilacyclohexane compound is converted to the dihalosilacyclohexane
compound by reaction with an electrophilic reagent.
11. A process according to claim 9, wherein the conversion of the step (1)
is effected by addition of a Lewis acid or by irradiation of actinic
light.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a process for preparing silacyclohexane compounds
which serve as a liquid crystal.
2. Description of the Prior Art
The liquid crystal display devices make use of optical anisotropy and
dielectric anisotropy of liquid crystal substances. Depending on the mode
of display, there are a variety of display systems including those of a
twisted nematic type (TN type), a supertwisted nematic type (STN type), a
super birefringence type (SBE type), a dynamic scattering type (DS type),
a guest/host type, a type of deformation of aligned phase (DAP type), a
polymer dispersion type (PD type), and an optical mode interference type
(OMI type). The most popular display device is one which is based on the
Schadt-Helfrich effect and has a twisted nematic structure.
Although the properties of the liquid substances used in these liquid
crystal devices depend, more or less, on the type of display, it is
commonly required that the liquid crystal substances have a wide range of
liquid crystal working temperatures and that they be stable against
moisture, air, light, heat, electric field and the like. Moreover, the
liquid crystal substances should desirably be low in viscosity and should
ensure a short address time, a low threshold voltage and a high contrast
in a cell.
As the liquid crystal display devices have wider utility in recent years,
the characteristic properties required for liquid crystal materials become
much severer. In addition, those characteristics which have never been
required for conventional liquid crystal substances are now expected such
as a lower drive voltage, a wider working temperature range which could
satisfy the needs for on-vehicle materials and an improvement in low
temperature performance.
Under these circumstances, we developed novel silacyclohexane-based liquid
crystal compounds which contain a silicon atom in the molecule so that the
characteristic properties for use as a liquid crystal substance are
improved. These liquid crystal compounds have been proposed, for example,
in co-pending U.S. application Ser. Nos. 08/377,961, filed Jan. 25, 1995
and 08/395,706, filed Feb. 28, 1995 (corresponding to European Patent
Application Nos. 95101167.5, filed Jan. 27, 1995 and 951029.8.1, filed
Mar. 1, 1995 and Korean Patent Application Nos. 95-1701, filed Jan. 28,
1995 and 95-4084, filed Feb. 28, 1995, respectively). These compounds of a
trans form are particularly useful as a liquid crystal compound. The
compounds obtained at the stage of preparation thereof are in the form of
a mixture of cis and trans isomers, which requires separation of the trans
isomer from the mixture.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a process for preparing liquid
crystal compounds predominantly in the form of a trans form.
It is another object of the invention to provide processes for the
selective preparation of silacyclohexane-based liquid crystal compounds of
a trans form.
The above objects can be achieved, according to one embodiment of the
invention, by a process for preparing a silacyclohexane compound, which
comprises the steps of:
(1) subjecting a diarylsilacyclohexane compound of the following general
formula (1)
##STR5##
wherein Ar and Ar' independently represent a phenyl group or a tolyl
group, and Q represents a group of the following formula (2)
##STR6##
in which
##STR7##
independently represent
##STR8##
wherein Y.sub.3 represents H, F or CH.sub.3 ;
##STR9##
represents
##STR10##
wherein Y.sub.1 and Y.sub.2 independently represent H, F or Cl; X
represents R or OR, in which each R represents a linear alkyl group having
from 1 to 10 carbon atoms, a branched alkyl group having from 3 to 8
carbon atoms, an alkoxyalkyl group having from 2 to 7 carbon atoms or an
alkenyl group having from 2 to 8 carbon atom, CN, F, Cl, CF.sub.3,
CF.sub.2 Cl, OCF.sub.3, OCHF.sub.2, OCF.sub.2 Cl, OCHFCl, (O).sub.m
CT.dbd.CX.sub.1 X.sub.2, or O(CH.sub.2).sub.r (CF.sub.2).sub.s X.sub.3
wherein m is a value of 0 or 1, T and X.sub.1 independently represent H, F
or Cl, X.sub.2 represents F or Cl, r and s are, respectively, a value of
0, 1 or 2 provided that r+s=2, 3 or 4, and X.sub.3 represents F or Cl; and
i1, i2 and i3 are, respectively, 0 or 1 provided that i1+i2+i3=1 and j1,
j2 and j3 are, respectively, a value of 0, 1 or 2 provided that
j1+j2+j3=0, 1 or 2, to conversion into a dihalosilacyclohexane compound of
the following general formula (3)
##STR11##
wherein each W represents a halogen, preferably Cl or Br;
(2) subjecting the compound of the formula (3) to further reaction with an
alcohol of the general formula, R'OH, wherein R' represents a linear alkyl
group having from 1 to 10 carbon atoms or a branched alkyl group having
from 3 to 8 carbon atoms, thereby obtaining a dialkoxysilacyclohexane
compound of the following general formula (4)
##STR12##
(3) reducing the compound of the formula (4) to obtain a
dihydrosilacyclohexane compound of the following general formula (5)
##STR13##
(4) subjecting the compound of the formula (5) to monohalogenation to
obtain a hydrohalosilacyclohexane compound of the following general
formula (6)
##STR14##
wherein W represents a halogen, preferably Cl or Br; and
(5) subjecting the compound of the formula (6) to reaction with an
organometallic reagent of the general formula, Q'--M, wherein (a) Q'
represents a group of the following formula (7)
##STR15##
in which
##STR16##
represents
##STR17##
wherein Y.sub.3 represents H, F or CH.sub.3 ;
##STR18##
represents
##STR19##
wherein Y.sub.1 and Y.sub.2 independently represent H, F or Cl; X'
represents R or OR, in which each R represents a linear alkyl group having
from 1 to 10 carbon atoms, a branched alkyl group having from 3 to 8
carbon atoms, an alkoxyalkyl group having from 2 to 7 carbon atoms or an
alkenyl group having from 2 to 8 carbon atoms, CN, F, Cl, CF.sub.3,
CF.sub.2 Cl, OCF.sub.3, OCHF.sub.2, OCF.sub.2 Cl, OCHFCl, (O).sub.m
CT.dbd.CX.sub.1 X.sub.2, or O(CH.sub.2).sub.r (CF.sub.2).sub.s X.sub.3
wherein m is a value of 0 or 1, T and X.sub.1 independently represent H, F
or Cl, X.sub.2 represents F or Cl, r and s are, respectively, a value of
0, 1 or 2 provided that r+s=2, 3 or 4, and X.sub.3 represents F or Cl; and
k1 and k2 are independently a value of 0 or 1 provided that k1+k2=1, m1
and m2 are independently represent a value of 0, 1 or 2 provided that
m1+m2=0, 1 or 2; and (b) M represents MgP or ZnP wherein P represents a
halogen, preferably Cl, Br or I, thereby obtaining a silacyclohexane
compound of the following general formula (I)
##STR20##
wherein Q' and Q have, respectively, the same meanings defined above.
According to another embodiment of the invention, there is also provided a
process for preparing a silacyclohexane compound of the above-defined
general formula (I) in which the step (2) of the process according to the
first embodiment is omitted, i.e. the compound of the general formula (3)
is reduced to obtain the compound of the general formula (5). More
particularly, the process of this embodiment comprises the steps of:
(1) subjecting a diarylsilacyclohexane compound of the following general
formula (1)
##STR21##
wherein Ar and Ar' independently represent a phenyl group or a tolyl
group, and Q represents a group of the following formula (2)
##STR22##
in which
##STR23##
independently represent
##STR24##
wherein Y.sub.3 represents H, F or CH.sub.3 ;
##STR25##
represents
##STR26##
wherein Y.sub.1 and Y.sub.2 independently represent H, F or Cl; X
represents R or OR, in which each R represents a linear alkyl group having
from 1 to 10 carbon atoms, a branched alkyl group having from 3 to 8
carbon atoms, an alkoxyalkyl group having from 2 to 7 carbon atoms or an
alkenyl group having from 2 to 8 carbon atoms, CN, F, Cl, CF.sub.3,
CF.sub.2 Cl, OCF.sub.3, OCHF.sub.2, OCF.sub.2 Cl, OCHFCl, (O).sub.m
CT.dbd.CX.sub.1 X.sub.2, or O(CH.sub.2).sub.r (CF.sub.2).sub.s X.sub.3
wherein m is a value of 0 or 1, T and X.sub.1 independently represent H, F
or Cl, X.sub.2 represents F or Cl, r and s are, respectively, a value of
0, 1 or 2 provided that r+s=2, 3 or 4, and X.sub.3 represents F or Cl; and
i1, i2 and i3 are, respectively, a value of 0 or 1 provided that
i1+i2+i3=1 and j1, j2 and j3 are, respectively, a value of 0, 1 or 2
provided that j1+j2+j3=0, 1 or 2, to conversion into a
dihalosilacyclohexane compound of the following general formula (3)
##STR27##
wherein each W represents a halogen, preferably Cl or Br;
(2) reducing the compound of the formula (3) to obtain a
dihydrosilacyclohexane compound of the following general formula (5)
##STR28##
(3) subjecting the compound of the formula (5) to monohalogenation to
obtain a hydrohalosilacyclohexane compound of the following general
formula (6)
##STR29##
wherein W represents a halogen, preferably Cl or Br; and
(4) subjecting the compound of the formula (6) to reaction with an
organometallic reagent of the general formula, Q'--M, wherein (a) Q'
represents a group of the following formula (7)
##STR30##
in which
##STR31##
represents
##STR32##
wherein Y.sub.3 represents H, F or CH.sub.3 ;
##STR33##
represents
##STR34##
wherein Y.sub.1 and Y.sub.2 independently represent H, F or Cl; X'
represents R or OR, in which each R represents a linear alkyl group having
from 1 to 10 carbon atoms, a branched alkyl group having from 3 to 8
carbon atoms, an alkoxyalkyl group having from 2 to 7 carbon atoms or an
alkenyl group having from 2 to 8 carbon atoms, CN, F, Cl, CF.sub.3,
CF.sub.2 Cl, OCF.sub.3, OCHF.sub.2, OCF.sub.2 Cl, OCHFCl, (O).sub.m
CT.dbd.CX.sub.1 X.sub.2, or O(CH.sub.2).sub.r (CF.sub.2).sub.s X.sub.3
wherein m is a value of 0 or 1, T and X.sub.1 independently represent H, F
or Cl, X.sub.2 represents F or Cl, r and s are, respectively, a value of
0, 1 or 2 provided that r+s=2, 3 or 4, and X.sub.3 represents F or Cl; and
k1 and k2 are independently a value of 0 or 1 provided that k 1+k2=1, m1
and m2 are independently represent a value of 0, 1 or 2 provided that
m1+m2=0, 1 or 2; and (b) M represents MgP or ZnP wherein P represents a
halogen, preferably Cl, Br or I, thereby obtaining a silacyclohexane
compound of the following general formula (I)
##STR35##
wherein Q' and Q have, respectively, the same meanings defined above.
According to a further embodiment of the invention, there is provided a
process for preparing a silacyclohexane compound of the above-defined
general formula (I) in which the steps (2) and (3) of the process
according to the first embodiment are omitted, i.e. the compound of the
general formula (3) is directly converted to a hydrohalosilacyclohexane
compound of the afore-indicated formula (6). More particularly, the
process of this embodiment comprises the steps of:
(1) subjecting a diarylsilacyclohexane compound of the following general
formula (1)
##STR36##
wherein Ar and Ar' independently represent a phenyl group or a tolyl
group, and Q represents a group of the following formula (2)
##STR37##
in which
##STR38##
independently represent
##STR39##
wherein Y.sub.3 represents H, F or CH.sub.3 ;
##STR40##
represents
##STR41##
wherein Y.sub.1 and Y.sub.2 independently represent H, F or Cl; X
represents R or OR, in which each R represents a linear alkyl group having
from 1 to 10 carbon atoms, a branched alkyl group having from 3 to 8
carbon atoms, an alkoxyalkyl group having from 2 to 7 carbon atoms or an
alkenyl group having from 2 to 8 carbon atoms, CN, F, Cl, CF.sub.3,
CF.sub.2 Cl, OCF.sub.3, OCHF.sub.2, OCF.sub.2 Cl, OCHFCl, (O).sub.m
CT.dbd.CX.sub.1 X.sub.2, or O(CH.sub.2).sub.r (CF.sub.2).sub.s X.sub.3
wherein m is a value of 0 or 1, T and X 1 independently represent H, F or
Cl, X.sub.2 represents F or Cl, r and s are, respectively, a value of 0, 1
or 2 provided that r+s=2, 3 or 4, and X.sub.3 represents F or Cl; and i1,
i2 and i3 are, respectively, a value of 0 or 1 provided that i1+i2+i3=1
and j1, j2 and j3 are, respectively, a value of 0, 1 or 2 provided that
j1+j2+j3=0, 1 or 2, to conversion into a dihalosilacyclohexane compound of
the following general formula (3)
##STR42##
wherein each W represents a halogen, preferably Cl or Br;
(2) reducing the compound of the formula (3) under conditions sufficient to
obtain a hydrohalosilacyclohexane compound of the following general
formula (6)
##STR43##
wherein W has the same meaning as defined above; and
(3) subjecting the compound of the formula (6) to reaction with an
organometallic reagent of the general formula, Q'--M, wherein (a) Q'
represents a group of the following formula (7)
##STR44##
in which
##STR45##
represents
##STR46##
wherein Y.sub.3 represents H, F or CH.sub.3 ;
##STR47##
represents
##STR48##
wherein Y.sub.1 and Y.sub.2 independently represent H, F or Cl; X'
represents R or OR, in which each R represents a linear alkyl group having
from 1 to 10 carbon atoms, a branched alkyl group having from 3 to 8
carbon atoms, an alkoxyalkyl group having from 2 to 7 carbon atoms or an
alkenyl group having from 2 to 8 carbon atoms, CN, F, Cl, CF.sub.3,
CF.sub.2 Cl, OCF.sub.3, OCHF.sub.2, OCF.sub.2 Cl, OCHFCl, (O).sub.m
CT.dbd.CX.sub.1 X.sub.2, or O(CH.sub.2).sub.r (CF.sub.2).sub.s X.sub.3
wherein m is a value of 0 or 1, T and X.sub.1 independently represent H, F
or Cl, X.sub.2 represents F or Cl, r and s are, respectively, a value of
0, 1 or 2 provided that r+s=2, 3 or 4, and X.sub.3 represents F or Cl; and
k1 and k2 are independently a value of 0 or 1 provided that k1+k2=1, m1
and m2 are independently represent a value of 0, 1 or 2 provided that
m1+m2=0, 1 or 2; and (b) M represents MgP or ZnP wherein P represents a
halogen, preferably Cl, Br or I, thereby obtaining a silacyclohexane
compound of the following general formula (I)
##STR49##
wherein Q' and Q have, respectively, the same meanings defined above.
DETAILED DESCRIPTION OF THE INVENTION
As is known in the art, ordinary liquid crystal compositions are in use in
the form of mixtures consisting of as many as 10 to 20 compounds. These
compounds contain homologues which have a substantially similar core or
skeletal structure only with a difference in folded chain length. With
existing hydrocarbon liquid crystal compositions, if the lengths of the
folded chains differ from one another, the starting material which is
employed at the most upstream stage is prepared to fix with respect to the
length of folded chain, from which an intended product is prepared through
several tens steps of reactions. In this connection, however, according to
the invention, it is possible to prepare silicon-containing liquid crystal
compounds whose length and type of folded chain can be arbitrarily
determined at a final step of a multistage reaction procedure. For known
hydrocarbon liquid crystal compounds, such a determination is not
possible. This is possible only for silicon-containing liquid crystal
compounds. Especially, in the field of applications of liquid crystal
compounds wherein a diversity of compounds having similar structures have
to be prepared, such a preparatory procedure as set out hereinabove
enables one to reduce the number of reaction steps as a whole, thus
leading to a very good economy.
The embodiments of the invention are described. It will be noted that Ar,
Ar', P, Q, Q', R, R', T, X, X', X.sub.1, X.sub.2, X.sub.3, Y.sub.1
-Y.sub.3, W, Y, Z, i1-i3, j1-j3, k1, k2, m1, and m2 which have,
respectively, been defined in the foregoing formulas have, respectively,
the same meanings as defined hereinbefore and may not be sometimes defined
again in formulas appearing hereinafter.
The dihalosilacyclohexane used in all the embodiments of the invention is
of the following formula (3)
##STR50##
This compound is prepared from a diarylsilacyclohexanone compound through a
diarylsilacyclohexane compound by use of an electrophilic reagent EW, in
which W represents a halogen, according to a procedure set out in Japanese
Patent Application No. 6-78125, filed Mar. 24, 1994 and not yet laid open.
This is particularly shown in the following reaction formula (8)
##STR51##
wherein Ar and Ar' independently represent a phenyl group or a tolyl
group, and Q represents a group of the general formula (2) defined
hereinbefore. In the formula (2), X may represent a group of R or OR along
with CN, F, Cl, CF.sub.3, CF.sub.2 Cl, OCF.sub.3, OCHF.sub.2, OCF.sub.2
Cl, OCHFCl, (O).sub.m CT.dbd.CX.sub.1 X.sub.2, or O(CH.sub.2).sub.r
(CF.sub.2).sub.s X.sub.3. In the case, each R represents a linear alkyl
group having from 1 to 10 carbon atoms, a branched alkyl group having from
3 to 8 carbon atoms, an alkoxyalkyl group having from 2 to 7 carbon atoms,
or an alkenyl group having from 2 to 8 carbon atoms.
Examples of the linear alkyl group having from 1 to 10 carbon represented
by R include methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl,
n-heptyl, n-octyl, nononyl and n-decyl. Examples of the branched alkyl
group having 3 to 8 carbon atoms include iso-propyl, 1-methylpropyl,
2-methylpropyl, sec-butyl, isobutyl, 1-methylbutyl, 2-methylbutyl,
3-methylbutyl, 1-methylpentyl, 2-methylpentyl, 3-methylpentyl,
1-ethylpentyl, 1-methylhexyl, 2-methylhexyl, 3-methylhexyl, 2-ethylhexyl,
3-ethylhexyl, 1-methylheptyl, 2-methylheptyl and 3-methylheptyl.
Examples of the alkoxyalkyl group having from 2 to 7 carbon atoms include
methoxymethyl, ethoxymethyl, propoxymethyl, butoxymethyl, pentoxymethyl,
hexyloxymethyl, methoxyethyl, ethoxyethyl, propoxyethyl, butoxyethyl,
methoxypropyl, ethoxypropyl, propoxypropyl, butoxypropyl, methoxybutyl,
ethoxybutyl, propoxybutyl, methoxypentyl and ethoxypentyl. Examples of the
alkenyl group include vinyl, 1-propenyl, allyl, 1-butenyl, 3-butenyl,
isoprenyl, 1-pentenyl, 3-pentenyl, 4-pentenyl, dimethylallyl, 1-hexenyl,
3-hexenyl, 5-hexenyl, 1-heptenyl, 3-heptenyl, 6-heptenyl and 7-octenyl.
The electrophilic reagents used for the reaction formula (8) include
halogens, hydrogen halides, metal halides, sulfonic derivatives, acid
halides, alkyl halides and the like. Preferably, there are mentioned
bromine, iodine, chlorine, iodine monochloride, hydrogen chloride,
hydrogen bromide, hydrogen iodide, mercury (II) chloride, trimethylsilyl
chlorosulfonate, acetyl chloride, acetyl bromide, benzoyl chloride,
t-butyl chloride and the like. In order to increase the reaction velocity,
Lewis acids such as aluminium chloride, zinc chloride, titanium
tetrachloride, boron trifiuoride and the like may be added to the reaction
system. Alternatively, the reaction system may be irradiated with actinic
light such as ultraviolet rays and/or visible rays.
Preferably, this reaction using the electrophilic agent is carried out at a
temperature of from 0.degree. to 80.degree. C., more preferably from
10.degree. to 40.degree. C.
The resultant dihalosilacyclohexane compound has two halogen atoms directly
bonded to the silicon atom, one of which can be converted to hydrogen atom
by using a reducing agent in a stoichiometric amount sufficient for
conversion of one halogen atom into a hydrogen atom. This is particularly
shown in the following reaction formula (9)
##STR52##
The reducing agents used include, for example, metal hydrides such as
sodium hydride, calcium hydride, trialkylsilanes, boranes,
dialkylaluminiums and the like, complex hydrides such as lithium aluminium
hydride, sodium borohydride, lithium borohydride, potassium borohydride,
tributylammonium borohydride and the like, and substituted hydrides
thereof such as lithium trialkoxyaluminium hydrides, sodium
di(methoxyethoxy)aluminium hydride, lithium triethylborohydride, sodium
cyanoborohydride and the like. The reduction reaction is preferably
effected at a temperature of from 0.degree. to 100.degree. C. In general,
the reduction reaction is carried out in a solvent such as diethyl ether,
tetrahydrofuran, dioxane, toluene, xylene, hexane, isooctane or the like.
The resultant hydrohalosilacyclohexane compound is then subjected to
carbon-silicon bonding reaction with an organometallic reagent of the
formula, Q'--M, wherein Q' and M have, respectively, the same meanings as
defined hereinbefore to obtain an intended silacyclohexane compound of the
general formula (I)
##STR53##
This reaction is shown in the following formula (10)
##STR54##
At the time of the above carbon-silicon reaction, a trans isomer useful as
a liquid crystal compound is obtained at high selectivity. This reaction
is preferably effected at a temperature of from 50.degree. to 150.degree.
C. for a time ranging from 0.1 to 5 hours until the reaction is completed.
Alternatively, the dihalosilacyclohexane compound obtained in the formula
(8) indicated hereinbefore may be converted into a dihydrosilacyclohexane
compound. To this end, one equivalent of the dihalosilacyclohexane
compound is reacted with two equivalents of a reducing agent as shown in
the reaction formula (11)
##STR55##
The reducing agents and reaction conditions in this case may be those used
in the reaction formula (9), respectively.
The resultant dihydrosilacyclohexane is reacted with a halogenating agent
in a stoichiometric amount sufficient for selective monohalogenation
thereby obtaining a hydrohalosilacyclohexane according to the following
general formula (12)
##STR56##
Finally, the intended silacyclohexane compound of the formula (I) is
obtained through the carbon-silicon bonding reaction as shown in the
aforeindicated formula (10)
##STR57##
The halogenating agents used in the formula (12) include, for example,
halogens such as chlorine, bromine, iodine, iodine chloride and the like,
copper chloride+copper iodide, silane halides, metal halides, halides of
sulfonic derivatives, alkyl halides and the like ordinarily employed
halogenating agents.
The process of this embodiment involves one additional step of the formula
(11) on comparison with the embodiment including the steps of the formulas
(8) and (9) wherein the hydrohalosilacyclohexane compound is directly
formed by the reduction shown in the formula (9). In this connection,
however, the hydrohalosilacyclohexane compound may be obtained in a better
yield in this embodiment depending on the chemical structure of Q, i.e.
the selectivity to the monohalogenation may be adversely influenced
depending on the chemical structure of the group, Q. Accordingly,
whichever process is selected depends on the chemical structure of Q to be
selected.
Still alternatively, the dihalosilacyclohexane compound obtained in the
afore-indicated formula (8) may be reacted with an alcohol for conversion
into a dialkoxysilacyclohexane compound as shown in the following reaction
formula (13)
##STR58##
wherein R' has the same meaning as defined before and preferably
represents a linear alkyl group having from 1 to 4 carbon atoms or a
branched alkyl group having from 3 or 4 carbon atoms. Examples of the
linear alkyl group and branched alkyl group are those mentioned with
respect to R of the formula (3). Preferable examples of the alcohol
represented by the formula, R'OH, include lower alcohols such as methanol,
ethanol, n-propyl alcohol, iso-propyl alcohol, n-butyl alcohol and the
like. In order to neutralize the resultant hydrogen halide, amines such as
triethylamine, urea and the like, or epoxy compounds such as propylene
oxide may be added to the reaction system. The reaction with the alcohol
is preferably effected at a temperature ranging from 0.degree. to
80.degree. C.
This embodiment include a larger number of steps than those two embodiments
set out hereinbefore and is advantageous in that when the
dihalosilacyclohexane compound is obtained from the diarylsilacyclohexane
compound in the afore-indicated formula (8), a solid catalyst such as
aluminum chloride is preferably used. If used, the catalyst can be readily
removed when the preparation is conducted through the step of preparing
the dialkoxysilacyclohexane compound. On the other hand, if the catalyst
is used and left in the step of the afore-indicated formula (10), it may
adversely influence the reaction. In this sense, the removal of the
catalyst is preferred.
The dialkoxysilacyclohexane compound is then reacted with a reducing agent
in an amount of two times by equivalent as great as that of the
dialkoxysilacyclohexane compound to obtain a dihydrosilacyclohexane
compound according to the following reaction formula (14)
##STR59##
The types of reducing agents and the reduction conditions are similar to
those set out hereinbefore with respect to the formula (9).
The thus obtained dihydrosilacyclohexane compound is subjected to
monohalogenation with a halogenating agent used in a stoichiometric amount
sufficient for the monohalogenation in a manner using a halogenating agent
as set out hereinbefore with respect to the afore-indicated formula (12).
This is particularly shown in the following reaction formula (15)
##STR60##
The resultant hydrohalosilacyclohexane compound is reacted with an
organometallic compound of the formula, Q'--M, in the same manner as in
the foregoing embodiments to obtain an intended silacyclohexane compound
(I)
##STR61##
The thus prepared compound may be further purified by a usual manner such
as recrystallization, chromatography or the like to an extent necessary
for practical applications, thereby obtaining a silacyclohexane-based
liquid crystal compound as an intended trans isomer, if necessary.
The present invention is more particularly described by way of examples.
PREPARATORY EXAMPLE 1
Preparation of
4-(trans-4-(3,4-difluorophenyl)cyclohexyl)-1,1-diphenyl-1-silacyclohexane
20.0 g of 3,4-difluoro-1-bromobenzene was dropped in a mixture of 3.0 g of
magnesium and 50 ml of tetrahydrofuran (hereinafter referred to simply as
THF), followed by refluxing for 3 hours to obtain a Grignard reagent. A
solution of 35.0 g of 4-(4,4-diphenyl-4-silacyclohexyl)cyclohexanone in 50
ml of THF was added to the Grignard reagent. After refluxing over 2 hours,
the reaction mixture was cooled down to room temperature and then charged
into an ammonium chloride aqueous solution, followed by extraction with
benzene. 1 g of p-toluenesulfonic acid was added to the benzene solution
or phase, after which while refluxing, generated water was separated and
removed. At the time when water was stopped distilling off, the mixture
was cooled down to room temperature. This mixture was poured into a sodium
hydrogencarbonate aqueous solution, followed by washing with brine, drying
and concentration by a usual manner. The resultant residue was purified
through silica gel chromatography to obtain
4-(4-(3,4-difluorophenyl)-3-cyclohexenyl)-1,1-diphenyl-1-silacyclohexane.
This product was dissolved in 200 ml of ethyl acetate, followed by
hydrogenation in the presence of 200 mg of a palladium-carbon catalyst at
a pressure of hydrogen of 0.5 MPa. After consumption of the theoretical
amount of hydrogen, the catalyst was removed by filtration and the
resultant filtrate was concentrated to obtain 42.0 g of
4-(trans-4-(3,4-difluorophenyl)cyclohexyl)-1,1-diphenyl-1-silacyclohexane.
The results of IR analysis are shown below.
IR (liquid film) .nu..sub.max : 2920, 2850, 1601, 1515, 1425, 1275, 1205,
1115, 980, 940 cm.sup.-1
EXAMPLE 1
Preparation of
trans-(4-(trans-4-(3,4-difluorophenyl)cyclohexyl)-1-n-pentyl-1-silacyclohe
xane
A solution, in 100 ml of dichloromethane, of 42.0 g of
4-(trans-4-(3,4-difluorophenyl)cyclohexyl)-1,1-diphenyl-1-silacyclohexane
obtained in Preparatory Example 1 was added to 250 ml of a dichloromethane
solution of 1.0 mol/liter of iodine monochloride at room temperature,
followed by agitation for 1 hour to obtain
4-(trans-4-(3,4-difluorophenyl)cyclohexyl)-1,1-dichloro-1-silacyclohexane.
Subsequently, a mixture of 50.0 g of isopropyl alcohol and 300 g of
triethylamine was added to the solution at room temperature, followed by
agitation under reflux for 1 hour. The resultant solution was
concentrated, after which 200 ml of hexane was added thereby permitting
secondarily produced hydrochloride to be settled down. The hydrochloride
was removed by filtration and the resultant filtrate was concentrated to
obtain a mixture of
4-(trans-4-(3,4-difluorophenyl)cyclohexyl)-1,1-diisopropoxy-1-silacyclohex
ane and acetophenone. This mixture was subjected to distillation under
reduced pressure to remove the acetophenone therefrom, and the residue was
dissolved in 100 ml of THF and added to a solution of 10.0 g of lithium
aluminium hydride in 100 ml of THF. The reaction mixture was agitated
under reflux for 1 hour, after which the mixture was poured into 200 ml of
5% hydrochloric acid and extracted with ethyl acetate. The resultant
extract was washed with brine, dried and concentrated by a usual manner,
followed by purification through silica gel chromatography to obtain 26.2
g of 4-(trans-4-(3,4-difluorophenyl)cyclohexyl)-1-silacyclohexane. The
results of IR analysis of the product are shown below.
IR (liquid film) .nu..sub.max : 2920, 2850, 2140, 1602, 1518, 1278, 1212,
1107, 942, 860, 818 cm.sup.-1
Thereafter, 25.0 g of
4-(trans-4-(3,4-difluorophenyl)cyclohexyl)-1-silacyclohexane, 23.0 g of
copper (II) chloride, and 1.5 g of copper (I) iodide were added to 200 ml
of diethyl ether, followed by agitation at room temperature for 8 hours to
obtain
4-(trans-4-(3,4-difluorophenyl)cyclohexyl)-1-chloro-1-silacyclohexane. The
copper salts were removed from the reaction mixture by filtration,
followed by dropping the resultant filtrate in 100 ml of a THF solution of
1 mole/liter of n-pentylmagnesium bromide at room temperature. The
reaction mixture was poured into 200 ml of 5% hydrochloric acid and
extracted with ethyl acetate. The resultant extract was washed with brine,
dried and concentrated by a usual manner, followed by purification through
silica gel chromatography to obtain 29.2 g (yield: 90%) of the intended
product. The product exhibited nematic liquid crystal properties at a
temperature ranging from 14.3.degree. to 71.6.degree. C. and was found to
be very useful as a liquid crystal substance. The results of IR analysis
are shown below.
IR (liquid film) .nu..sub.max : 2923, 2845, 2092, 1608, 1520, 1296, 1213,
1113, 891, 825, 808 cm.sup.-1
EXAMPLE 2
Preparation of
trans-(4-(trans-4-(3,4-difluorophenyl)cyclohexyl)-1-n-propyl-1-silacyclohe
xane
The general procedure of Example 1 was repeated except that a THF solution
of n-propylmagnesium bromide was used in place of the THF solution of
n-pentylmagnesium bromide, thereby obtaining the captioned product in a
similar yield. The product exhibited nematic liquid crystal properties at
a temperature between 20.3.degree. and 79.3.degree. C. and was found to be
very useful as a liquid crystal substance. The results of IR analysis are
shown below.
IR (liquid film) .nu..sub.max : 2924, 2854, 2100, 1606, 1518, 1279, 987,
887, 843, 818 cm.sup.-1
As will be apparent from Examples 1 and 2, the change of only one step
permitted liquid crystal compounds to be prepared as having lengths of
alkyl groups which differed from each other. The preparation of liquid
crystal compounds having different lengths of alkyl groups by changing
only one step will not be possible for known, silicon-free liquid crystal
compounds.
PREPARATORY EXAMPLE 2
Preparation of 4-(4,4-diphenyl-silacyclohexyl)-4'-fluorobiphenyl
A solution of 25.1 g 4-bromo-4'-fluorobiphenyl in 100 ml of THF was dropped
in a mixture of 3.0 g of magnesium and 50 ml of THF, followed by refluxing
for 3 hours to obtain a Grignard reagent. A solution of 25.0 g of
1,1-diphenyl-1-silacyclohexanone in 50 ml of THF was added to the Grignard
reagent. After refluxing over 2 hours, the reaction mixture was cooled
down to room temperature and then charged into an ammonium chloride
aqueous solution, followed by extraction with benzene. 1 g of
p-toluenesulfonic acid was added to the benzene solution, after which
while refluxing, generated water was separated and removed. At the time
when water was stopped distilling off, the mixture was cooled down to room
temperature. This mixture was poured into a sodium hydrogencarbonate
aqueous solution, followed by washing with brine, drying and concentration
by a usual manner. The resultant residue was purified through silica gel
chromatography to obtain
4-(4,4-diphenyl-4-silacyclohexenyl)-4'-fluorobiphenyl. This product was
dissolved in 200 ml of ethyl acetate, followed by hydrogenation in the
presence of 200 mg of a palladium-carbon catalyst at a pressure of
hydrogen of 0.5 MPa. After consumption of the theoretical amount of
hydrogen, the catalyst was removed by filtration and the resultant
filtrate was concentrated to obtain 41.5 g of
4-(4,4-diphenyl-4-silacyclohexyl)-4'-fluorobiphenyl.
EXAMPLE 3
Preparation of trans-4-(4-n-propyl-4-silacyclohexyl)-4'-fluorobiphenyl
A solution, in 100 ml of dichloromethane, of 41.0 g of
4-(4,4-diphenyl-4-silacyclohexyl)-4'-fluorobiphenyl obtained in
Preparatory Example 2 was added to 250 ml of a dichloromethane solution of
1.0 mol/liter of iodine monochloride at room temperature, followed by
agitation for 1 hour to obtain
4-(4,4-dichloro-4-silacyclohexyl)-4'-fluorobiphenyl. The reaction solution
was concentrated and the resultant residue was dissolved in 100 ml of THF,
which was then added to 100 ml of a THF solution of 10.0 g of lithium
aluminium hydride. The reaction mixture was agitated under reflux for 1
hour and then poured into 200 ml of 5% hydrochloric acid, followed by
extraction with ethyl acetate. The resultant extract was washed with
brine, dried and concentrated by a usual manner, followed by purification
through silica gel chromatography to obtain 23.6 g of
4-(4-silacyclohexyl)-4'-fluorobiphenyl.
Subsequently, 23.0 g of 4-(4-silacyclohexyl)-4'-fluorobiphenyl, 23.0 g of
copper (II) chloride, and 1.5 g of copper (I) iodide were added to 200 ml
of diethyl ether, followed by agitation at room temperature for 8 hours to
obtain 4-(4-chloro-4-silacyclohexyl)-4'-fluorobiphenyl. The copper salts
were removed from the reaction mixture by filtration, followed by dropping
the resultant filtrate in 100 ml of a THF solution of 1 mole/liter of
n-propylmagnesium bromide at room temperature. The reaction mixture was
poured into 200 ml of 5% hydrochloric acid and extracted with ethyl
acetate. The resultant extract was washed with brine, dried and
concentrated by a usual manner, followed by purification through silica
gel chromatography to obtain 25.5 g (yield: 96%) of the intended product.
The product exhibited nematic liquid crystal properties at a temperature
ranging from 80.2.degree. to 119.3.degree. C. and was found to be very
useful as a liquid crystal substance. The results of IR analysis of the
product are shown below.
IR (liquid film) .nu..sub.max : 2854, 2198, 2087, 1604, 1497, 1238, 987,
889, 816 cm.sup.-1
EXAMPLE 4
Preparation of trans-4-(4-n-pentyl-4-silacyclohexyl)-4'-fluorobiphenyl
The general procedure of Example 3 was repeated except that a THF solution
of n-pentylamgnesium bromide was used in place of the THF solution of
n-propylmagnesium bromide, thereby obtaining the captioned product in a
similar yield. The product exhibited nematic liquid crystal properties at
a temperature between 71.degree. and 118.degree. C. and was found to be
very useful as a liquid crystal substance. The results of IR analysis are
shown below.
IR (liquid film) .nu..sub.max : 2916, 2852, 2096, 1495, 1238, 982, 883,
835, 810 cm.sup.-1
As will be apparent from Examples 3 and 4, the change of only one step
permitted liquid crystal compounds to be prepared as having lengths of
alkyl groups which differed from each other. The preparation of liquid
crystal compounds having different lengths of alkyl groups by changing
only one step will not be possible for known, silicon-free liquid crystal
compounds. Accordingly, with silicon-containing liquid crystal compounds,
it is possible to reduce the number of preparation steps to a significant
extent, with good economy.
PREPARATORY EXAMPLE 3
Preparation of 4-n-pentyl-1,1-diphenyl-1-silacyclohexane
12.0 g of potassium t-butoxide was added to a mixture of 41.0 g of
n-pentyltriphenylphosphonium bromide and 200 ml of THF, thereby preparing
a ylide solution which was orange in color. A solution of 28.0 g of
4,4-diphenyl-4-silacyclohexyl carbaldehyde in 50 ml of THF was added to
the ylide solution. After agitation at room temperature for 2 hours, the
reaction mixture was poured into iced water and extracted with ethyl
acetate. The resultant extract was washed with brine, dried and
concentrated by a usual manner, followed by addition of hexane to the
resultant residue. The resulting crystals of triphenylphosphine oxide were
removed by filtration and the filtrate was concentrated. The resultant
residue was purified through silica gel chromatography to obtain
4-(n-pentylidene)-1,1-diphenyl-1-silacyclohexane. This product was
dissolved in 200 ml of ethyl acetate, followed by hydrogenation in the
presence of 200 mg of a platinum oxide catalyst at a pressure of hydrogen
of 0.1 MPa. After consumption of the theoretical amount of hydrogen, the
catalyst was removed by filtration and the resultant filtrate was
concentrated to obtain 31.5 g of 4-n-pentyl-1-diphenyl-1-silacyclohexane.
EXAMPLE 5
Preparation of
trans-1-(trans-2-((3,4-difluorophenyl)cyclohexyl)ethyl)-4-n-pentyl-1-silac
yclohexane
14.6 g of acetyl chloride was added to a solution, in 200 ml of
dichloromethane, of 30.0 g of 4-n-pentyl-1,1-diphenyl-1-silacyclohexane
obtained in Preparatory Example 3 and 24.8 g of aluminium chloride at room
temperature, followed by agitation for 1 hour to obtain a mixture of
4-n-pentyl-1,1-dichloro-1-silacyclohexane and acetophenone. The reaction
mixture was concentrated, after which the acetophenone was distilled off
under reduced pressure. The residue was dissolved in 100 ml of THF, to
which a solution of 10.0 g of lithium aluminium hydride in 100 ml of THF
was added. The reaction mixture was agitated under reflux for 1 hour,
followed by pouring into 200 ml of 5% hydrochloric acid and extraction
with ethyl acetate. The resultant extract was washed with brine, dried and
concentrated by a usual manner, followed by purification through silica
gel chromatography to obtain 15.0 g of 4-n-pentyl-1-silacyclohexane.
Thereafter, 15.0g of 4-n-pentyl-1-silacyclohexane, 24.2 g of copper (II)
chloride, and 1.6 g of copper (I) iodide were added to 200 ml of diethyl
ether, followed by agitation at room temperature for 8 hours to obtain
4-n-pentyl-1-chloro-1-silacyclohexane. The copper salts were removed from
the reaction mixture by filtration, after which the resultant filtrate was
dropped in 100 ml of a THF solution of 1 mole/liter of
trans-2-((3,4-difluorophenyl)cyclohexyl)ethylmagnesium bromide at room
temperature. The reaction mixture was poured into 200 ml of 5%
hydrochloric acid and extracted with ethyl acetate. The resultant extract
was washed with brine, dried and concentrated by a usual manner, followed
by purification through silica gel chromatography to obtain 32.1 g of the
intended product. The product exhibited nematic liquid crystal properties
at a temperature ranging from 14.7.degree. to 28.9.degree. C. The results
of IR analysis are shown below.
IR (liquid film) .nu..sub.max : 2920, 2850, 2098, 1608, 1518, 1286, 887,
862, 816 cm.sup.-1
EXAMPLE 6
Preparation of
trans-1-(trans-2-((4-fluorophenyl)cyclohexyl)ethyl)-4-n-propyl-1-silacyclo
hexane
The general procedure of Example 5 was repeated except that a THF solution
of trans-2-((4-fluorophenyl)cyclohexyl)ethylmagnesium bromide was used in
place of the THF solution of
trans-2-((3,4-difluorophenyl)cyclohexyl)ethylmagnesium bromide, thereby
obtaining the intended compound.
Thus, the change of only one step enabled one to prepare liquid crystal
compounds whose polar groups differed from each other. With known,
silicon-free liquid crystal compounds, it was not possible to prepare
liquid crystal compounds whose polar groups differed in type by changing
only one step. For the preparation of silicon-containing liquid crystal
compounds, the number of preparation steps could be reduced significantly
with good economy.
PREPARATORY EXAMPLE 4
Preparation of 4-(2-fluorophenyl)ethyl)-1,1-diphenyl-1-silacyclohexane
12.0 g of potassium t-butoxide was added to a mixture of 45.0 g of
p-fluorobenzyltriphenylphosphonium bromide and 200 ml of THF, thereby
preparing a ylide solution which was orange in color. A solution of 28.0 g
of 4,4-diphenyl-4-silacyclohexyl carbaldehyde in 50 ml of THF was added to
the ylide solution. After agitation at room temperature for 2 hours, the
reaction mixture was poured into iced water and extracted with ethyl
acetate. The resultant extract was washed with brine, dried and
concentrated by a usual manner, followed by addition of hexane to the
resultant residue. The resulting crystals of triphenylphosphine oxide were
removed by filtration and the filtrate was concentrated. The resultant
residue was purified through silica gel chromatography to obtain
4-(2-(p-fluorophenyl)ethenyl)-1,1-diphenyl-1-silacyclohexane. This product
was dissolved in 200 ml of ethyl acetate, followed by hydrogenation in the
presence of 200 mg of a platinum oxide catalyst at a pressure of hydrogen
of 0.1 MPa. After consumption of the theoretical amount of hydrogen, the
catalyst was removed by filtration and the resultant filtrate was
concentrated to obtain 36.5 g of
4-(2-(p-fluorophenyl)ethyl)-1,1-diphenyl-1-silacyclohexane.
EXAMPLE 7
Preparation of
trans-4-(trans-4-(2-(4-fluorophenyl)ethyl)-1-silacyclohexyl)-1-n-propylcyc
lohexane
15.1 g of acetyl chloride was added to a solution, in 200 ml of
dichloromethane, of 36.0 g of
4-(2-fluorophenyl)ethyl)-1,1-diphenyl-1-silacyclohexane obtained in
Preparatory Example 4 and 25.6 g of aluminium chloride at room
temperature, followed by agitation for 1 hour to obtain a mixture of
4-(2-(p-fluorophenyl)ethyl)-1,1-dichloro-1-silacyclohexane and
acetophenone. A mixture of 40 g of ethanol and 60 g of triethylamine was
added to the solution at room temperature. The resultant reaction mixture
was concentrated, after which 200 ml of hexane was added to permit
secondarily produced triethylamine hydrochloride to be precipitated. This
precipitate was removed by filtration and the resultant filtrate was
concentrated, followed by removal of the acetophenone by distillation
under reduced pressure to obtain 28.5 g of
4-(2-(p-fluorophenyl)ethyl)-1,1-diethoxy-1-silacyclohexane. This product
was dissolved in 100 ml of THF and added to a solution of 10.0 g of
lithium aluminium hydride in 100 ml of THF. The reaction mixture was
agitated under reflux for 1 hour and then poured into 200 ml of 5%
hydrochloric acid, followed by extraction with ethyl acetate. The
resultant extract was washed with brine, dried and concentrated, followed
by purification through silica gel chromatography to obtain 20.1 g of
4-(2-(p-fluorophenyl)ethyl)-1-silacyclohexane. Thereafter, 20.0 g of
4-(2-(p-fluorophenyl)ethyl)-1-silacyclohexane, 24.2 g of copper (II)
chloride, and 1.6 g of copper (I) iodide were added to 200 ml of diethyl
ether, followed by agitation at room temperature for 8 hours to obtain
4-(2-(p-fluorophenyl)ethyl)-1-chloro-1-silacyclohexane. The copper salts
were removed from the reaction mixture by filtration, after which the
resultant filtrate was dropped in 100 ml of a THF solution of 1 mole/liter
of 4-n-propylcyclohexylmagnesium bromide at room temperature. The reaction
mixture was poured into 200 ml of 5% hydrochloric acid and extracted with
ethyl acetate. The resultant extract was washed with brine, dried and
concentrated by a usual manner, followed by purification through silica
gel chromatography to obtain 21.2 g (68%) of the intended product. The
product exhibited nematic liquid crystal properties at a temperature
between 40.degree. and 56.7.degree. C. The results of IR analysis are
shown below.
IR (KBr, disc) .nu..sub.max : 2916, 2841, 2089, 1510, 1223, 891, 820
cm.sup.31 1
EXAMPLE 8
Preparation of
trans-4-(trans-4-(2-(4-fluorophenyl)ethyl)-1-silacyclohexyl)-1-n-pentylcyc
lohexane
The general procedure of Example 7 was repeated except that a THF solution
of 4-n-pentylcyclohexylmagnesium bromide was used in place of the THF
solution of 4-n-propylcyclohexylmagnesium bromide, thereby obtaining the
captioned compound. The results of IR analysis and measurement of
transition temperatures are shown below.
IR (liquid film) .nu..sub.max : 2916, 2845, 2094, 1510, 1223, 887, 823
cm.sup.-1
Transition temperatures: C21N67I (i.e. C-N transition temperature of
21.degree. C. and N-I transition temperature of 67.degree. C.)
PREPARATORY EXAMPLE 5
Preparation of 4-(p-fluorophenyl)-1,1-diphenyl-1-silacyclohexane
16.5 g of p-fluorobromobenzene was dropped in a mixture of 2.6 g of
magnesium and 50 ml of THF, followed by refluxing for 3 hours to obtain a
Grignard reagent. A solution of 26.0 g of 4,4-diphenyl-4-silacyclohexanone
in 50 ml of THF was added to the Grignard reagent. After refluxing for 2
hours, the reaction mixture was cooled down to room temperature and poured
into an ammonium chloride aqueous solution, followed by extraction with
benzene. 1 g of p-toluenesulfonic acid was added to the benzene solution.
While refluxing, generated water was separated and removed. At the time
when the generation of water was stopped, the reaction mixture was cooled
down to room temperature. Subsequently, the reaction mixture was charged
into a sodium hydrogencarbonate aqueous solution, washed with brine, dried
and concentrated by a usual manner. The resultant residue was purified
through silica gel chromatography to obtain 33.0 g of
4-(p-fluorophenyl)-1,1-diphenyl-1-sila-3-cyclohexene. This product was
dissolved in 200 ml of ethanol and hydrogenated in the presence of 200 mg
of a palladium-carbon catalyst under a hydrogen pressure of 0.5 MPa. After
consumption of the theoretical amount of hydrogen, the catalyst was
removed by filtration and the resultant filtrate was concentrated to
obtain 33.1 g of 4-(p-fluorophenyl)-1,1-diphenyl-1-silacyclohexane. The
results of IR analysis are shown below.
IR (KBr, disc) .nu..sub.max : 2915, 2850, 1601, 1422, 1215, 1108, 975, 875,
825 cm.sup.-1
EXAMPLE 9
Preparation of trans-4-(p-fluorophenyl)-1-n-heptyl-1-silacyclohexane
15.3 g of acetyl chloride was added to a solution, in 200 ml of
dichloromethane, of 30.0 g of
4-(p-fluorophenyl)-1,1-diphenyl-1-silacyclohexane obtained in Preparatory
Example 5 and 25.4 g of aluminium chloride at room temperature, followed
by agitation for 1 hour. The reaction mixture was subjected to
distillation under reduced pressure to obtain 21.0 g of
4-(p-fluorophenyl)-1,1-dichloro-1-silacyclohexane. This product was
dissolved in 100 ml of THF and added to a solution of 10.0 g of lithium
aluminium hydride in 100 ml of THF. The reaction mixture was agitated
under reflux for 30 minutes, after which the mixture was poured into 200
ml of 5% hydrochloric acid and extracted with ethyl acetate. The ethyl
acetate solution or extract was washed with brine, dried and concentrated
by a usual manner, followed by purification through silica gel
chromatography to obtain 14.8 g of 4-(p-fluorophenyl)-1-silacyclohexane.
The results of IR analysis are shown below.
IR (liquid film) .nu..sub.max : 2920, 2850, 2140, 1600, 1508, 1222, 1157,
941, 881, 862, 829 cm.sup.-1
Subsequently, 11.8 g of bromine was added to a solution of 14.0 g of
4-(p-fluorophenyl)-1-silacyclohexane in 100 ml of dichloromethane to
obtain 4-(p-fluorophenyl)-1-bromo-1-silacyclohexane. The reaction solution
was concentrated and the resultant residue was dissolved in 50 ml of
diethyl ether, followed by dropping in 100 ml of a THF solution of 1
mole/liter of n-heptylmagnesium bromide at room temperature. The reaction
mixture was poured into 200 ml of 5% hydrochloric acid and extracted with
ethyl acetate. The resultant ethyl acetate solution was washed with brine,
dried and concentrated, followed by purification through silica gel
chromatography to obtain 19.0 g (yield: 90%) of the intended product. The
results of IR and NMR analyses are shown below.
IR (liquid film) .nu..sub.max : 2920, 2100, 1510, 1458, 1408, 1228, 985,
887, 820 cm.sup.-1 13 C-NMR (67.5 MHz, CDCl.sub.3): 10.56 (s), 12.13 (s),
14.11 (s), 22.74 (s), 24.44 (s), 29.08 (s), 31.85 (s), 83.19 (s), 33.45
(s), 46.92 (s), 114.90 (d), 127.89 (d), 144.81 (d), 161.09 (d) ppm
EXAMPLE 10
Preparation of trans-4-(p-fluorophenyl)-1-n-pentyl-1-silacyclohexane
The general procedure of Example 9 was repeated except that a THF solution
of 4-n-pentylmagnesium bromide was used was used in place of the THF
solution of n-heptylmagnesium bromide, thereby obtaining the captioned
compound.
EXAMPLE 11
Preparation of
4-(trans-4-(trans-4-n-propylcyclohexyl)-4-silacyclohexyl)-1-fluorobenzene
In the same manner as in Example 9, 21.0 g of
4-(p-fluorophenyl)-1,1-dichloro-1-silacyclohexane was obtained from
4-(p-fluorophenyl)-1,1-diphenyl-1-silacyclohexane obtained in Preparatory
Example 5. This product was dissolved in 100 ml of THF and added to a
solution of 0.8 g of lithium aluminium hydride in 100 ml of THF at
0.degree. C. The reaction mixture was agitated as it is for 30 minutes,
after which the reducing agent was removed by filtration. The resultant
filtrate was concentrated to obtain
4-(p-fluorophenyl)-1-chloro-1-silacyclohexane. The thus obtained product
was dissolved in 50 ml of THF, followed by dropping in 100 ml of a THF
solution of 1 mole/liter of 4-n-propylcyclohexylmagnesium bromide at room
temperatures. The reaction mixture was poured into 200 ml of 5%
hydrochloric acid and extracted with ethyl acetate. The ethyl acetate
solution was washed with brine, dried and concentrated, followed by
purification through silica gel chromatography to obtain 20.0 g of the
intended product. This product exhibited nematic liquid crystal properties
at a temperature between 56.2.degree. C. and 110.9.degree. C. and was
found to be very useful as a liquid crystal substance. The results of IR
analysis are shown below.
IR (KBr, disc) .nu..sub.max : 2914, 2843, 2102, 1605, 1508, 1225, 985, 887,
879, 812 cm.sup.-1
EXAMPLE 12
Preparation of
4-(trans-4-(trans-4-n-butylcyclohexyl)-4-silacyclohexyl)-1-fluorobenzene
The general procedure of Example 11 was repeated except that a THF solution
of 4-n-butylcyclohexylmagnesium bromide was used in place of the THF
solution of 4-n-propylcyclohexylmagnesium bromide, thereby obtaining the
captioned compound. The compound exhibited nematic liquid crystal
properties at a temperature between 40.1.degree. C. and 106.7.degree. C.
and was found to be very useful as a liquid crystal substance. The results
of IR analysis are shown below.
IR (liquid film) .nu..sub.max : 2924, 2919, 2846, 2102, 1604, 1508, 1225,
985, 812 cm.sup.-1
EXAMPLE 13
Preparation of
4-(trans-(2-(4-(trans-4-n-propylcyclohexyl)ethyl)-4-silacyclohexyl)-1-fluo
robenzene
In the same manner as in Example 9, 21.0 g of
4-(p-fluorophenyl)-1,1-dichloro-1-silacyclohexane was obtained from
4-(p-fluorophenyl)-1,1-diphenyl-1-silacyclohexane obtained in Preparatory
Example 5. A mixture of 50.0 g of methanol and 30 g of triethylamine was
added to the solution obtained above, followed by agitation under reflux
for 1 hour. The resultant solution was concentrated, to which 200 ml of
hexane was added thereby permitting secondarily produced hydrochloride to
be precipitated. The precipitate was removed by filtration and the
resulting filtrate was concentrated to obtain a mixture of
4-(p-fluorophenyl)-1,1-dimethoxy-1-silacyclohexane and acetophenone. The
mixture was subjected to distillation under reduced pressure to remove the
acetophenone therefrom. The resultant residue was dissolved in 100 ml of
THF and added to a solution of 10.0 g of lithium aluminium hydride in 100
ml of THF. The reaction mixture was agitated under reflux for 1 hour,
which was poured into 200 ml of 5% hydrochloric acid and extracted with
ethyl acetate. The ethyl acetate solution was washed with brine, dried and
concentrated by a usual manner, followed by purification through silica
gel chromatography to obtain 14.7 g of
4-(p-fluorophenyl)-1-silacyclohexane. Subsequently, 14.0 g of
4-(p-fluorophenyl)-1-silacyclohexane was added to 100 ml of toluene, into
which chlorine gas was blown to obtain
4-(p-fluorophenyl)-1-chloro-1-silacyclohexane. This solution was dropped
in 100 ml of a THF solution of 1 mole/liter of
trans-2-(4-n-propylcyclohexyl)ethylmagnesium bromide at room temperature.
The reaction mixture was charged into 200 ml of 5% hydrochloric acid and
extracted with ethyl acetate. The ethyl acetate solution was washed with
brine, dried and concentrated, followed by purification through silica gel
chromatography to obtain 20.8 g of the intended product. The thus obtained
product exhibited nematic liquid crystal properties at a temperature
between 49.1.degree. C. and 62.9.degree. C. and was found to be very
useful as a liquid crystal substance.
IR (KBr, disc) .nu..sub.max : 2908, 2848, 2096, 1603, 1510, 1223, 985, 887,
831, 814 cm.sup.-1
EXAMPLE 14
Preparation of
trans-4-(2-(p-fluorophenyl)ethyl)-1-n-pentyl-1-silacyclohexane
Hydrogen chloride gas was blown into a solution, in 200 ml of benzene, of
36.0 g of trans-4-(2-(p-fluorophenyl)ethyl)-1,1-diphenyl-1-silacyclohexane
and 5.0 g of aluminium chloride to obtain 30.0 g of
trans-4-(2-(p-fluorophenyl)ethyl)-1,1-dichloro-1-silacyclohexane. The
product was dissolved in 100 ml of THF, which was added to a solution of
1.0 g of lithium aluminium hydride serving as a reducing agent in 100 ml
of THF at 0.degree. C. The reaction mixture was agitated as it is for 30
minutes, followed by removal of the reducing agent and concentration of
the resultant filtrate to obtain
4-(2-(p-fluorophenyl)ethyl)-1-chloro-1-silacyclohexane. This product was
dissolved in 50 ml of THF and dropped in 100 ml of a THF solution of 1
mole/liter of n-pentylmagnesium bromide at room temperature, followed by
extraction with ethyl acetate. The ethyl acetate solution was washed with
brine, dried and concentrated by a usual manner, followed by purification
through silica gel chromatography to obtain 26.8 g of the intended
product. The results of IR analysis are shown below.
IR (liquid film) .nu..sub.max : 2918, 2852, 2098, 1601, 1510, 1223, 887,
823 cm.sup.-1
EXAMPLE 15
Preparation of trans,
trans-2-fluoro-4-(4-n-pentyl-4-silacylohexyl)-4'-(4-n-propylhexyl)biphenyl
The general procedure of Example 1 was repeated using
2-fluoro-4-(4,4-diphenyl-4-silacyclohexyl)-4'-(trans-4-n-propylcyclohexyl)
biphenyl and a THF solution of n-pentylmagnesium bromide, thereby obtaining
the intended compound. The results of measurement of liquid crystal
temperature ranges and IR analysis are shown below.
Liquid crystal temperature range: C79.0S95.0N247.0I (i.e. C-N transition
temperature of 79.0.degree. C., S-N transition temperature of 95.0.degree.
C. and N-I transition temperature of 247.0.degree. C.)
IR (KBr, disc) .nu..sub.max : 2920, 2848, 2098, 1493, 1404, 1194, 987, 887,
812 cm.sup.-1
EXAMPLE 16
Preparation of trans,
trans-4-(4-methoxycylohexyl)-1-n-propyl-1-silacyclohexane
The general procedure of Example 1 was repeated using
4-(trans-4-methoxycyclohexyl)-1,1-diphenyl-1-silacyclohexane and a THF
solution of n-propylmagnesium bromide, thereby obtaining the intended
compound. The results of measurement of liquid crystal temperature ranges
and IR analysis are shown below.
Liquid crystal temperature range: C<-60N-40.0I (i.e. C-N transition
temperature of lower than -60.degree. C, and N-I transition temperature of
-40.0.degree. C.)
IR (liquid film) .nu..sub.max : 2928, 2856, 2820, 2098, 1452, 1103, 989,
887, 843, 820 cm.sup.-1
EXAMPLE 17
Preparation of
4-(2-(trans-4-n-pentyl-4-silacyclohexyl)ethyl)-3',4'-difluorobiphenyl
The general procedure of Example 1 was repeated using
4-(2-(4,4-diphenyl-4-silacyclohexyl)ethyl)-3',4'-difluorobiphenyl and a
THF solution of n-pentylmagnesium bromide, thereby obtaining the intended
compound. The results of measurement of liquid crystal temperature ranges
and IR analysis are shown below. Liquid crystal temperature range:
C38.6N58.2I (i.e. C-N transition temperature of 38.6.degree. C., and N-I
transition temperature of 58.2.degree. C.)
IR (liquid film) .nu..sub.max : 2920, 2850, 2100, 1605, 1504, 1311, 1267,
814 cm.sup.-1
EXAMPLE 18
Preparation of trans,
trans-4-(4-(4-n-propyl-4-silacyclohexyl)cyclohexyl)-3',4'-difluorobiphenyl
The general procedure of Example 1 was repeated using
4-(trans-4-(4,4-diphenyl-4-silacyclohexyl)cyclohexyl)-3',4'-difluorobiphen
yl and a THF solution of n-propylmagnesium bromide, thereby obtaining the
intended compound. The results of measurement of liquid crystal
temperature ranges and IR analysis are shown below.
Liquid crystal temperature range: C82.7S107.5N229.1I (i.e. C-S transition
temperature of 82.7.degree. C., S-N transition temperature of
107.5.degree. C. and N-I transition temperature of 229.1.degree. C.)
IR (KBr, disc) .nu..sub.max : 2916, 2848, 2104, 1533, 1506, 1279, 985, 889,
845, 814 cm.sup.-1
EXAMPLE 19
Preparation of 4-(trans-4-n-pentyl-4-silacyclohexyl)-2,4"-difluoroterphenyl
The general procedure of Example 1 was repeated using
4-(4,4-diphenyl-4-silacyclohexyl)-2,4"-difluoroterphenyl and a THF
solution of n-pentylmagnesium bromide, thereby obtaining the intended
compound. The results of measurement of liquid crystal temperature ranges
and IR analysis are shown below.
Liquid crystal temperature range: C87.8S135.0N250.3I (i.e. C-S transition
temperature of 87.8.degree. C., S-N transition temperature of
135.0.degree. C. and N-I transition temperature of 250.3.degree. C.)
IR (KBr, disc) .nu..sub.max : 2918, 2846, 2106, 1487, 1223, 887, 816 cm-1
EXAMPLE 20
Preparation of
trans-4-(4-n-pentyl-4-silacyclohexyl)-2-fluoro-4'-(2-(3,4-difluorophenyl)e
thyl)biphenyl
The general procedure of Example 1 was repeated using
4-(4,4-diphenyl-4-silacyclohexyl)-2-fluoro-4'-(2-(3,4-difluorophenyl)ethyl
)biphenyl and a THF solution of n-pentylmagnesium bromide, thereby
obtaining the intended compound. The results of measurement of liquid
crystal temperature ranges and IR analysis are shown below.
Liquid crystal temperature range: C49.5(SA)50.6N150.5I (i.e. C-(SA)
transition temperature of 49.5.degree. C., (SA)-N transition temperature
of 50.6.degree. C. and N-I transition temperature of 150.5.degree. C.)
IR (KBr, disc) .nu..sub.max : 2920, 2102, 1518, 1491, 1404, 1290, 1286,
1120, 889, 818 cm-1
EXAMPLE 21
Preparation of trans,
trans-4-(2-(4-(4-n-propyl-4-silacyclohexyl)cyclohexyl)ethyl)-4'-chloro-3'-
fluorobiphenyl
The general procedure of Example 1 was repeated using
4-(2-(trans-4-(4,4-diphenyl-4-silacyclohexyl)cyclohexyl)ethyl)-4'-chloro-3
'-fluorobiphenyl a THF solution of n-propylmagnesium bromide, thereby
obtaining the intended compound. The results of measurement of liquid
crystal temperature ranges and IR analysis are shown below.
Liquid crystal temperature range: C63.3N208.0I (i.e. C-N transition
temperature of 63.3.degree. C. and N-I transition temperature of
208.0.degree. C.)
IR (KBr, disc) .nu..sub.max : 2920, 2850, 2096, 1560, 1481, 1200, 1070,
982, 889, 845, 805 cm.sup.-1
As will be apparent from the foregoing description, trans isomers of
silacyclohexane compounds having a silicon atom in the molecule can be
selectively prepared, according to the invention, as exhibiting liquid
crystal properties. The thus prepared silacyclohexane liquid crystal
compounds are very useful as a material for liquid crystal displays.
Additionally, when Si-containing liquid crystal compounds are prepared
according to the process of the invention, the length and type of folded
chain can be determined at a final step of a multi-stage procedure. In the
field of applications of liquid crystals wherein a number of liquid
crystal compounds have to be prepared to form a liquid crystal
composition, it will not be possible to prepare such a liquid crystal
composition making use of Si-free liquid crystal compounds alone.
According to the invention, a diversity of Si-containing liquid crystal
compounds can be efficiently, economically prepared.
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